"Given the long and well-documented history of torture of political activists by China's security forces, there is every reason to fear for the safety of those recently detained," Brad Adams, the group's Asia director, said in a statement

Amnesty's Mark Allison said it was ironic that China had imposed a complete media blackout on the situation in Tibet at a time when authorities had promised complete media freedom in the run up to the Olympics.

"The crackdown clearly is not the kind of image China wanted to promote to the outside world, he said

China, Allison said, was "on notice from the international community" that it could not use methods it has used in the past against Tibetan protesters, such as torture and arbitrary detentions.